IAT and MAP sensor

[hex0rz]

Okay, so I have been wondering if my sensors were any good. So, I only managed to pull my IAT sensor and it only looked a little dirty. Nothing like what mike has in his pictures.I was gonna use a DMM to measure the ohms according to the temp. and I could not even get a reading from it. I checked the DMM and the DMM is fine. Is the IAT sensor bad?I did not have a socket to pull the MAP sensor. I need to go buy one but I'm confused about the size. Its definitely not 1 1/16".So I called o'reilly's and they quoted me $30 for the IAT sensor and $114 for the MAP sensor!Anyone also know if I can get these for cheaper? Would either one of them cause my mpg's to fall as well??

[Mopar1973Man]

Apparently the sensor is good because you didn't say anything about error codes or CEL lights. Little common sense. So the sensor has to be in the realm of normal values other than that the sensor would of thrown a code. So now go back and figure out what you did wrong during your testing.

[hex0rz]

Apparently the sensor is good because you didn't say anything about error codes or CEL lights. Little common sense. So the sensor has to be in the realm of normal values other than that the sensor would of thrown a code. So now go back and figure out what you did wrong during your testing.

Alright, so I rechecked the IAT sensor with the DMM and still got nothing for an ohm reading. I even checked to see if it had continuity and it did not say it had it. Isn't the sensor supposed to provide continuity? Even if the sensor is stil functioning, what about it reading inaccurately and it says the air is really colder than it is and does not change? That would create an overfuel condition, would it not?

[Yankneck696]

MAny cheaper DMMs need to be set into the right range. You need the K ohm range.Otherwise, they will just read OL (Out of limit)

[98whitelightnin]

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[Mopar1973Man]

Alright, so I rechecked the IAT sensor with the DMM and still got nothing for an ohm reading. I even checked to see if it had continuity and it did not say it had it. Isn't the sensor supposed to provide continuity? Even if the sensor is stil functioning, what about it reading inaccurately and it says the air is really colder than it is and does not change? That would create an overfuel condition, would it not?

IAT has no real change to fueling it effect more of the timing curve than fueling. Like myself I don't use the IAT sensor at all mine is unplugged and I stuff a rheostat in the plug for tuning ability for MPG's more so.

[diesel4life]

If your map was bad you would have some driveability issues, along with a cel. What is your truck doing thats causing you problems?

[Ilikeoldfords]

Hey mike, what does that rheostat do for your mpgs? How does it effect driveabiltity? Very noticeable differences? Sorry im off the OP, just really want to know...

[Mopar1973Man]

Hey mike, what does that rheostat do for your mpgs? How does it effect driveabiltity? Very noticeable differences? Sorry im off the OP, just really want to know...

Increases MPG because it give the illusion of being summer temperatures. Truthfully warmer air always produces better MPGs over colder air. Driveabiltity basically there is not much difference. The IAT fooler all it does is change the timing table.

[rancherman]

Increases MPG because it give the illusion of being summer temperatures. Truthfully warmer air always produces better MPGs over colder air. .

MPG's are better due to what? a denser air charge? A buttload of money has been spent by the masses 'buying the ultimate CAI ' over the years... with claims of 'more power, more mpgs'... Shoot, over at ramforumz thats ALL they talk about! (ok, possibly the newest add on cupholder too) Or was the better mpg's gained because of warmer weather caused the vehicle to roll easier? (fluids were 'thinner' quicker)... tires were more flexible.. etc. Or warmer air potentially holds more H20.. (akin to water injection)? * jus kickin a sleepin dog here* Or, running a winter blend fuel? who knows what actually is getting pumped into our tanks in the winter! I'll burn about 1-2 gallons more per hour in my tractors when I'm running blended. 20-25% increase in consumption.

[Yankneck696]

By my understanding, the computer changes the timing in colder weather for emissions. Fooling the computer in cold weather bypasses that programming & gives you close to summer mileage even with winter blend. I did the 143* fooler & got great MPGs across the country.Ed

[flagmanruss]

As I posted previously... I bought an extension harness for the IAT plug, cut it in the center & extended into the cab, installed a toggle on the knee panel. I turn the IAT back to stock to start... The "Wait to Start" light works normally as does the grid heaters. Starts up normally. Once it's running I flip the switch on the IAT fooler, which uses a resistor with (if memory serves me) a 143* value... equivent to a warmed up engine. It's worth about 1mpg in cold weather... on my truck. "Cold Air Intakes" are popular & sell well. CAI is a hold over from naturally aspirated gasoline race cars, where they did/do work. What modern consumers fail to consider is the differences between those cars & modern smogged cars... with IAT sensors. Modern fuel injected cars run far leaner than my old favorite carbureted engines... which gives them the high rated mpgs... but is why the computers richen the mix for cold engines. Now consider diesels... fired by the heat of compression. Then consider, that most of our trucks are intercooled (charge cooled between the turbo & the intake). THEN consider that the CTD has a water jacketed intake to warm the incoming air. Overall, I don't believe the CAIs do anything to help a diesel. Winter Fronts (fitted pieces blocking the grill) to keep warm air under the hood are a popular topic on this site. BHAFs draw warm underhood air...

[Mopar1973Man]

MPG's are better due to what? a denser air charge? A buttload of money has been spent by the masses 'buying the ultimate CAI ' over the years... with claims of 'more power, more mpgs'... Shoot, over at ramforumz thats ALL they talk about! (ok, possibly the newest add on cupholder too) Or was the better mpg's gained because of warmer weather caused the vehicle to roll easier? (fluids were 'thinner' quicker)... tires were more flexible.. etc. Or warmer air potentially holds more H20.. (akin to water injection)? * jus kickin a sleepin dog here* Or, running a winter blend fuel? who knows what actually is getting pumped into our tanks in the winter! I'll burn about 1-2 gallons more per hour in my tractors when I'm running blended. 20-25% increase in consumption.

So with my winter front I'm gaining more warmer air under the hood aiming to reach 100*F as a minimum for IAT temps. With my winter front I typically see roughly +50*F gain over outside temps so like right now its 32*F so it would be 82*F at the IAT. Close... Then also the IAT fooler on top of it Quadzilla tech even admitted the idea is solid because stable IAT temps will keep the timing table from jumping around. Also that ECM starts to retard timing slightly but then like a Edge Comp module can take advantage of the slack and push the timing forward again because the Edge Comp can modify the timing table after the ECM. Even yesterday with temp as cold as 21-25*F for day time high, winterized fuel, etc. I still got 20.5 MPG. Not bad If I say so myself. So winterize fuel, wind drag and thicker fluids excuse is now blown out of the water. There is a difference between HP/TQ tuning and Economy tuning. For HP/TQ your going to be running high boost pressures creating huge amount of compressor heat for a period of time down a quarter mile track. You looking to cram as much air into the cylinder as possible to make power so yes cold air is the way to go. But for economy tunning where you boost pressure typically float 2-5 PSI and there is no heat created by the turbo and the outside air is freezing cold passing over the intercooler. This retards the burn rate of the fuel. So now adding warmer air to the manifold bring the fuel burn rate back up and give you better economy numbers again.

[flagmanruss]

Mike makes a good point. Are we building race cars / trucks? Or are we building efficient economical trucks? One that gets good mpgs & then goes to work towing our toys or whatever.

[rancherman]

I agree too, 'cai's' should of been actually named 'air flow enhancers'. COLD had nothing to do with what they did. (pulling air from between the frame and exaust??) really? Ok, Ok, they can come in pretty colors! Anytime we pull air down a length of pipe, it does straighten out flow... but too much adds a friction factor too. So, the BHAF rises to the top!I was just trying to play devil's advocate, mike.. consider me 'blown out of the water'.

[Mopar1973Man]

I was just trying to play devil's advocate, mike.. consider me 'blown out of the water'.

Naw... Just makes me think hard in explaining my point a bit better.

[rancherman]

Naw... Just makes me think hard in explaining my point a bit better.

No problem! I guess I was correlating super dense air with 'efficiency'. My old snowmobile, and all my chainsaws run like BANSHEE'S when it's 0* F !!! I googled 'dense vs. warm' air charge, and the best scenario explaining better 'efficiency' with warm air is: "vechicles with O2 sensors will sniff the extra O2, (in cold dense air) and then add more fuel to hold proper ratio". Therefore reducing mpg's. (makes sense to me). 'rate of burn' is different too. So, if we take the same O2 - richer dense air, and run it thru our diesels, perhaps the 'rate of combustion' is slightly higher... (too quick) for optimum mpg? No doubt coldest air possible for max brake hp is needed!! but you are correct on 'max hp' also means 'max fuel' too!

[Mopar1973Man]

My old snowmobile, and all my chainsaws run like BANSHEE'S when it's 0* F !!!

Different animal again. Because it first off naturally aspirated and number two the fuel doesn't require activate heat energy to fire the fuel it uses a spark plug to ignite the fuel. Then on top of that gasoline flash point is seriously low so its easy to ignite regardless of outside temperature.

So now looking back at diesels you need glow plugs or grid heater to warm the air enough to even start it. Then your trying to fire the fuel on the active heat energy created by the cylinder compression. Then the fuel itself has to be ignited by autoignition temperature (compression) and not flash point (spark plug). So the colder the air gets the harder it is to ignite the fuel. So to compensate for this is why the manifold is pre-heated by coolant, grid heaters, and hotter thermostats compared to previous years since the 24V SO engine has the LOWEST compression ratio to all other Cummins engines at 16.3:1 (HO is 17.0:1) so the heated air is a welcomed sight.

The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the source of ignition is removed.

The flash point is not to be confused with the autoignition temperature, which does not require an ignition source, or the fire point, the temperature at which the vapor continues to burn after being ignited. Neither the flash point nor the fire point is dependent on the temperature of the ignition source, which is much higher.

The flash point is often used as a descriptive characteristic of liquid fuel, and it is also used to help characterize the fire hazards of liquids. “Flash point” refers to both flammable liquids and combustible liquids. There are various standards for defining each term. Liquids with a flash point less than 60.5 °C (140.9 °F) or 37.8 °C (100.0 °F)—depending upon the standard being applied—are considered flammable, while liquids with a flash point above those temperatures are considered combustible.^[1]

[Ilikeoldfords]

Increases MPG because it give the illusion of being summer temperatures. Truthfully warmer air always produces better MPGs over colder air. Driveabiltity basically there is not much difference. The IAT fooler all it does is change the timing table.

So with the timing set for warmer temps, is there any performance loss since there is still cooler air going into the engine? If not, why even bother putting an IAT sensor in?

[Mopar1973Man]

All for EPA and CARB reasons...